From: Yan Zhao <yan.y.zhao@intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<x86@kernel.org>, <alex.williamson@redhat.com>,
<kevin.tian@intel.com>, <iommu@lists.linux.dev>,
<pbonzini@redhat.com>, <seanjc@google.com>,
<dave.hansen@linux.intel.com>, <luto@kernel.org>,
<peterz@infradead.org>, <tglx@linutronix.de>, <mingo@redhat.com>,
<bp@alien8.de>, <hpa@zytor.com>, <corbet@lwn.net>,
<joro@8bytes.org>, <will@kernel.org>, <robin.murphy@arm.com>,
<baolu.lu@linux.intel.com>, <yi.l.liu@intel.com>
Subject: Re: [PATCH 5/5] iommufd: Flush CPU caches on DMA pages in non-coherent domains
Date: Thu, 16 May 2024 10:32:43 +0800 [thread overview]
Message-ID: <ZkVwS8n7ARzKAbyW@yzhao56-desk.sh.intel.com> (raw)
In-Reply-To: <ZkUeWAjHuvIhLcFH@nvidia.com>
On Wed, May 15, 2024 at 05:43:04PM -0300, Jason Gunthorpe wrote:
> On Wed, May 15, 2024 at 03:06:36PM +0800, Yan Zhao wrote:
>
> > > So it has to be calculated on closer to a page by page basis (really a
> > > span by span basis) if flushing of that span is needed based on where
> > > the pages came from. Only pages that came from a hwpt that is
> > > non-coherent can skip the flushing.
> > Is area by area basis also good?
> > Isn't an area either not mapped to any domain or mapped into all domains?
>
> Yes, this is what the span iterator turns into in the background, it
> goes area by area to cover things.
>
> > But, yes, considering the limited number of non-coherent domains, it appears
> > more robust and clean to always flush for non-coherent domain in
> > iopt_area_fill_domain().
> > It eliminates the need to decide whether to retain the area flag during a split.
>
> And flush for pin user pages, so you basically always flush because
> you can't tell where the pages came from.
As a summary, do you think it's good to flush in below way?
1. in iopt_area_fill_domains(), flush before mapping a page into domains when
iopt->noncoherent_domain_cnt > 0, no matter where the page is from.
Record cache_flush_required in pages for unpin.
2. in iopt_area_fill_domain(), pass in hwpt to check domain non-coherency.
flush before mapping a page into a non-coherent domain, no matter where the
page is from.
Record cache_flush_required in pages for unpin.
3. in batch_unpin(), flush if pages->cache_flush_required before
unpin_user_pages.
next prev parent reply other threads:[~2024-05-16 2:33 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 6:18 [PATCH 0/5] Enforce CPU cache flush for non-coherent device assignment Yan Zhao
2024-05-07 6:19 ` [PATCH 1/5] x86/pat: Let pat_pfn_immune_to_uc_mtrr() check MTRR for untracked PAT range Yan Zhao
2024-05-07 8:26 ` Tian, Kevin
2024-05-07 9:12 ` Yan Zhao
2024-05-08 22:14 ` Alex Williamson
2024-05-09 3:36 ` Yan Zhao
2024-05-16 7:42 ` Tian, Kevin
2024-05-16 14:07 ` Sean Christopherson
2024-05-20 2:36 ` Tian, Kevin
2024-05-07 6:20 ` [PATCH 2/5] KVM: x86/mmu: Fine-grained check of whether a invalid & RAM PFN is MMIO Yan Zhao
2024-05-07 8:39 ` Tian, Kevin
2024-05-07 9:19 ` Yan Zhao
2024-05-07 6:20 ` [PATCH 3/5] x86/mm: Introduce and export interface arch_clean_nonsnoop_dma() Yan Zhao
2024-05-07 8:51 ` Tian, Kevin
2024-05-07 9:40 ` Yan Zhao
2024-05-20 14:07 ` Christoph Hellwig
2024-05-21 15:49 ` Jason Gunthorpe
2024-05-21 16:00 ` Jason Gunthorpe
2024-05-22 3:41 ` Yan Zhao
2024-05-28 6:37 ` Christoph Hellwig
2024-05-07 6:21 ` [PATCH 4/5] vfio/type1: Flush CPU caches on DMA pages in non-coherent domains Yan Zhao
2024-05-09 18:10 ` Alex Williamson
2024-05-10 10:31 ` Yan Zhao
2024-05-10 16:57 ` Alex Williamson
2024-05-13 7:11 ` Yan Zhao
2024-05-16 7:53 ` Tian, Kevin
2024-05-16 8:34 ` Tian, Kevin
2024-05-16 20:31 ` Alex Williamson
2024-05-17 17:11 ` Jason Gunthorpe
2024-05-20 2:52 ` Tian, Kevin
2024-05-21 16:07 ` Jason Gunthorpe
2024-05-21 16:21 ` Alex Williamson
2024-05-21 16:34 ` Jason Gunthorpe
2024-05-21 18:19 ` Alex Williamson
2024-05-21 18:37 ` Jason Gunthorpe
2024-05-22 6:24 ` Tian, Kevin
2024-05-22 12:29 ` Jason Gunthorpe
2024-05-22 14:43 ` Alex Williamson
2024-05-22 16:52 ` Jason Gunthorpe
2024-05-22 18:22 ` Alex Williamson
2024-05-22 23:26 ` Tian, Kevin
2024-05-22 23:32 ` Jason Gunthorpe
2024-05-22 23:40 ` Tian, Kevin
2024-05-23 14:58 ` Jason Gunthorpe
2024-05-23 22:47 ` Alex Williamson
2024-05-24 0:30 ` Tian, Kevin
2024-05-24 13:50 ` Jason Gunthorpe
2024-05-22 3:33 ` Yan Zhao
2024-05-22 3:24 ` Yan Zhao
2024-05-22 12:26 ` Jason Gunthorpe
2024-05-24 3:07 ` Yan Zhao
2024-05-16 20:50 ` Alex Williamson
2024-05-17 3:11 ` Yan Zhao
2024-05-17 4:44 ` Alex Williamson
2024-05-17 5:00 ` Yan Zhao
2024-05-07 6:22 ` [PATCH 5/5] iommufd: " Yan Zhao
2024-05-09 14:13 ` Jason Gunthorpe
2024-05-10 8:03 ` Yan Zhao
2024-05-10 13:29 ` Jason Gunthorpe
2024-05-13 7:43 ` Yan Zhao
2024-05-14 15:11 ` Jason Gunthorpe
2024-05-15 7:06 ` Yan Zhao
2024-05-15 20:43 ` Jason Gunthorpe
2024-05-16 2:32 ` Yan Zhao [this message]
2024-05-16 8:38 ` Tian, Kevin
2024-05-16 9:48 ` Yan Zhao
2024-05-17 17:04 ` Jason Gunthorpe
2024-05-20 2:45 ` Yan Zhao
2024-05-21 16:04 ` Jason Gunthorpe
2024-05-22 3:17 ` Yan Zhao
2024-05-22 6:29 ` Yan Zhao
2024-05-22 17:01 ` Jason Gunthorpe
2024-05-27 7:15 ` Yan Zhao
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